- Impaired renal function as determined from serum creatinine levels, using the following formulas35: adult male Ccr = (140 -age) X weight in kilograms/(72 X serum creatinine in milligrams per deciliter); and adult female Ccr = [(140 - age) X weight in kilograms/(72 X serum creatinine in milligrams per deciliter)] X 0.85,whereCcr indicates creatinine clearance.